Screwdriver Antennas
 

The "Screwdriver" antennas by Hi-Q, TarHeel or High Sierra look very
interesting for HOA restricted locations. Does anyone have any
experience with one of these antennas? Also, does anyone have
experience using one as a base rather than mobile?

Thanks for any advice, jimbo

jimbo wrote:
The "Screwdriver" antennas by Hi-Q, TarHeel or High Sierra look very
interesting for HOA restricted locations. Does anyone have any
experience with one of these antennas? Also, does anyone have
experience using one as a base rather than mobile?

HighSierra makes one optimized for base operation. In
general, a base station is not usually limited to 13.5
ft. as is a mobile, and any addition to the length of
a very short antenna is an improvement.
--
73, Cecil http://www.qsl.net/w5dxp


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On 7 Feb 2005 08:49:00 -0800, "jimbo" wrote:
Also, does anyone have experience using one as a base rather than mobile?

Hi Jimbo,

You need only to consider that in your base application, you need as
much linear/mass equivalency to a truck/car frame to reproduce the
same results. It has been long observed that these highly specialized
antennas are in fact a tuned ground/counterpoise/radial in comparison
to the larger radiating surfaces of a truck or car.

If you think of them in these terms, you can allow invention and
available structures to solve more problems when you bolt one of these
to them.

73's
Richard Clark, KB7QHC

Hi Jimbo,

I've had good luck with my High Sierra HS-1800/Pro in just the
application you mention. You can take a look at:

http://www.qrz.com/w4tqt

73, Ron W4TQT

jimbo wrote:
The "Screwdriver" antennas by Hi-Q, TarHeel or High Sierra look very
interesting for HOA restricted locations. Does anyone have any
experience with one of these antennas? Also, does anyone have
experience using one as a base rather than mobile?

Thanks for any advice, jimbo

On 7 Feb 2005 08:49:00 -0800, "jimbo" wrote:

The "Screwdriver" antennas by Hi-Q, TarHeel or High Sierra look very
interesting for HOA restricted locations. Does anyone have any
experience with one of these antennas? Also, does anyone have
experience using one as a base rather than mobile?

Thanks for any advice, jimbo


I don't have experience with them base or mobile except to have been
on a trip with someone who has one on his truck. The antenna is
great. If you must have a compromise antenna, putting one of these on
the roof, maybe with the coil disguised in what looks like a vent,
might be a great antenna.

As I understand it, you will want to use as many tuned radials around
the antenna as you can get away with, at least two per band (four if
possible) for maximum signal. However, if that isn't possible, you
may consider grounding it to a large metal surface that surrounds the
antenna.

I don't know of an efficient way to hide one in a tree, but someone
here might have an idea that will be useful. Since it tunes itself,
you won't need a tuner and 50 ohm coax will be sufficient.

Chances are you will need to add some form of one-to-one balun (UNUN)
or hang a suitable number of ferrite beads on the coax next to the
antenna to prevent radiation from traveling back down the coax.

I have heard a lot of good reports from people that use them. I
understand that there are about three grades of the screwdriver
antennas. The smaller ones have more loss than the larger ones. It
is up to your budget as to whether you want to pay for that extra
little bit of signal you get with the larger antennas.

I wish you the best on it.

73

--
73 for now
Buck
N4PGW

On 9 Feb 2005 17:33:28 -0800, "jimbo" wrote:

I know that I want full band coverage 10-160, and I only have 100 watts
from my transmitter. So, I can't have an antenna that "eats" 90 percent
of my transmitter ourput.

Hi Jimbo,

The simple numbers are radiation resistance and Ohmic resistance.
Which is larger? Answer that and you have a simple answer. What are
their proportions? Answer that and you have a more complex answer.
Think of a voltage divider (now a power divider).

Now ask yourself, what is the radiation resistance? What is the Ohmic
resistance? For quarterwave and smaller antennas, simple formulas
abound (or tables are available) for radiation resistance. For Ohmic
resistance, this is a function of materials and construction. In this
last regard, it only takes a loose wire, or screw and this resistance
climbs through the roof.

Let's put that into context. For a 12' vertical radiator operating on
160M, you have a 4/160th's wavelength radiator. Radiation resistance
is running on the order of 1/4th Ohm. If you manage to hold all Ohmic
resistance to that value, or lower (everywhere - in TOTAL) then you
verge on 50% efficiency, or better.

Your Mileage May Vary.

73's
Richard Clark, KB7QHC

Hi Jimbo,

Check out: http://www.eham.net/reviews/detail/640

It is for Don W6AAQ's (who is the father of the
screwdriver) version.

Great antenna and half the price of all the others. I
have been using one of his for about 5 years.
73 Larry WA9VRH



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I have a High Sierra Sequoia and have used it with great success. You need a
good radial setup for optimal use, I made a set of eight 10FT long #12AWG
stranded which I arranged in a spoke around the antenna.. I use this for
mobile/portable setup; e-comm and field day. I have a mount on my deck rail
and 144 sq ft of chicken wire under the deck for a ground plane; but the
ground mounted antenna and radials work more efficiently.

I have a Carolina Windom strung up in the trees at home, black wire, fed
with coax buried from the house to the tree line. HOA has never noticed I
have an antenna up.

"jimbo" wrote in message
ups.com...
The "Screwdriver" antennas by Hi-Q, TarHeel or High Sierra look very
interesting for HOA restricted locations. Does anyone have any
experience with one of these antennas? Also, does anyone have
experience using one as a base rather than mobile?

Thanks for any advice, jimbo

Thanks for all of the great replies! I think one of these antennas is
going to work for my "stealth" antenna. I have read the various web
sites that offer "screwdriver" antennas until my eyes are crossing.
Everyone seems to be trashing eveyone else. Very hard to determine who
is straight and who is bull-------. Can anyone offer some insight into
stuff like coil diameter vs coil length vs "radiation efficiency" vs
anything?

I know that I want full band coverage 10-160, and I only have 100 watts
from my transmitter. So, I can't have an antenna that "eats" 90 percent
of my transmitter ourput. So what should I look for in a "screwdriver"
antenna that will give me the best performance with my specifications
and limitations?

Thanks for any advice, jimbo

Richard Clark wrote:
.. Let's put that into context. For a 12' vertical radiator operating on
160M, you have a 4/160th's wavelength radiator. Radiation resistance
is running on the order of 1/4th Ohm. If you manage to hold all Ohmic
resistance to that value, or lower (everywhere - in TOTAL) then you
verge on 50% efficiency, or better.

And ground losses are likely to be in the neighborhood of ten ohms
or about 2.5% efficiency.
--
73, Cecil http://www.qsl.net/w5dxp


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